In research and development, as well as commercial applications of nucleic acid biomarkers, it is desirable to extract high quality nucleic acids from biological samples in a consistent, reliable, and practical manner. An object of the present invention is therefore to provide a method for quick and easy isolation of nucleic acid-containing particles from biological samples such as body fluids, e.g., spinal fluid, and extraction of high quality nucleic acids from the isolated particles. The method of the invention may be suitable for adaptation and incorporation into a compact device or instrument for use in a laboratory or clinical setting, or in the field.